Propeller



I. B. FLOWERS.

PROPELLER. PFLICATION FILED SEPT. 2.2, 1920.

,405,910, Patented Feb.7, 1922.

UNITED STA'ILE PATENT OFFICE.

PROPELLER.

Specification of Letters-Patent.

Patented Feb. 7, 1922.

Application filed September 22,A 1920. Serial No. 411,979.

To all whom t may concern.'

Be it known that I, JOHN BENJAMIN FLOWERS, a citizen of the United States, residing at 339 Hamilton St., Albany, in the county of Albany and State of New York, have invented certain new and useful Improvements in Propellers, of which the following is a specification.

This invention relates to Propellers generally and more particularly to a propeller which will provide a uniform thrust and which will operate with comparatively little noise. A study of the cause of vropeller noise shows that at least one half t ereof is due to the pulse of air caused by each propeller blade of the propellers of the present type during each revolution when turning under power. The air in front of the blade in its rotation, is highly compressed, is forced past the propeller, and rushes into Vthe low pressure area created directly behind the blade as it progresses with its rotation. While theair is still in violent disturbance behind the blade it is struck by the second blade in its rotation. This rush of air to the low pressure area together with the impact of the following blade upon the disturbed air there creates a very violent disturbance or pulsation, with the noise inciu dent thereto, and the propeller itself is also thrown into a violent vibration.

Obviously, with the propellers of the types at present used, that 1s of a discontinuous spiral, as the two, three, and four blade of propellers now in use, it would be impossible to do away with this propeller noise. It is the purpose of this invention to provide a propeller with a comparatively uninterrupted and uniform thrust from front to rear, which will operate with but little vibration and noise.

Most of the noise of the propeller operation being due to the pulse of air caused by each blade, it is proposed to obviate the same by re-designing the propeller to give a constant thrust over the entire area covered by lthe propeller durin one revolution. This propeller blade shou d havek a diameter equal to the diameter of a circle described by the tip of the usual propeller blade.

It is proposed that the propeller have the shape of a double threaded screw and the blade will be in the form of a thin sheet of corrugated steel of extremely high tensile strength in order to stand the great centrifugal force.

xd ampe d Since a large part of the noise'of the propeller operation is due to the vibrations of the blade itself it is believed that that also could be eliminated by this construction, for as the thin steel blade over the entire revolution of the propeller will ride on a cushion of air, the vibrations will be critically during the entiie revolution.

A noiseless propeller is highly desirable for commercial planes for it has been found that the noise of the present type of pro-y peller is very objectionable to passengers. For military use it is necessary to do away with this propeller noise or the enemy will be fore-warned of the approach of the airplane. The use of noiseless propellers will, therefore, vastly increase the use of airplanes for reconnaissance.

T his invention is primarily intended as an improvement for propellers for use in aircraft but the inventor does not limit himself thereto. Y

In the accompanying drawings:

Fig. l is a top view in perspective with portion broken away to show spoke arrangemen f Fig. 2 is a front elevation of the and shaft;v

Fig. 3 is aside elevation ofy a portion of the propeller to show the detail of attachment of the spokes and blade to the shaft.

Referring to the figures in detail the propeller consists of two driving portions, spiral in shape and of substantially 360O each in extent and attached by means of spokes to the shaft. l is a propeller shaft which is attached to the outer driving ortion 3 of the propeller by spokes 2. he driving portions 3 are each built of corrugated sheet metal of high tensile strength and are crimped with a T-shaped upset at the inner ed e as 4 to provide means for fastening to t e spokes and at the outer edge as at 5 in a manner to provide rigidity to the structure of the'blade. The end of the spokes 2 are externally screw threaded and adapted for the reception of fastening nuts 6 and keys 8 for securing a driving portion 3 to a shaft 1. The driving ortion 3 has a cut-away portion 7 to provid?, space for the installation and adjustment of nuts 6. Spokes 2 are fastened in any desired manner to the propeller shaft and are, in the illustrated embodiment, inset and brazed to the shaft.

The driving portion is of such structure propeller as to extend trom the outer periphery of the propeller inwardly to a point substantiallyVV one-half the way tothe sha-tt. It has been found that the only useful thrust is Vperformed by such a portion of a propeller forV v balanced as nearly as possible by' means oi nuts 6 and Washers 11, 'which may be supplied as shovvn.v Y

`My device operates as follows: By reason of the fact that the driving portions of my propeller extend throughout the Whole cycle of 360O a thrust of uniform force willbe produced throughout the Whole thereof. This willv provide for a continuous air stream Which will be tree from the pulses caused by the beati-ng of the blades of the present type of propellers and will do away With the vi-k bration of the propeller that would be incident to such pulses. It will be seen', then, that the noise of propeller operation will thus be greatly diminished and a uniform thrust with its consequent benets obtained.

I claim :l v Y 1. In a propeller, a shaft, a driving portion of material of low relative thickness formed in two spiral blades of approximately 360 extension each, means connecting said driving portion to said shaft, and adjustable Y means 'for balancing the saine.

2. In aV propeller, a shaft, an outer driving portion in the forni of spiral blade ap` proximately 3600 in extent, aV plurality of' kspokes projecting from the lshafttoward the blade and having ustable connection With the latter, and' balancing nuts threaded on the spokes for engagement with the blade.

3. In a propeller, a shaft, driving portions of material oi low relative thickness and of high tensile strength formedV in two spiral blades of approximately 360o extension each, spokes for connecting said blades to the shaft, and means 'fori stream-lining such spokes in aline of' the spiral of the outer driving portion. Y f

4t. In a propel of material of low relativelthiekne'ss and oi' high tensile strength Vformed in two spiral blades of approximately 360 extension'ea'ch, spokes for connecting said blades f, to theV ler, ya shaft, drivingrportions sha-tt, and means. for stream-lining k'such spokes in the line of the spiral' of the outer drivingportion, said means being comprised of Ya lighter material than that yused inj the outer driving portion.

5. In aY propeller, a shaftand an outer, driving portion ofA material of ,high tensile strength, means connecting the's'ame, andan inner driving portionof lighter material;l

6. In a' propeller, a shaft, an equal driving portion of material of high tensile. strength, crimped to provider-additional'strength and an inner drivingportion of lighter material. Y In testimony whereof I have aiiixed my signature. f Y

- Joiin BENJAMIN imovvn'ns. -j- 

